Symmetric microwave filter and microwave integrated circuit merging the same

Abstract

A microwave filter is disposed on a substrate. The microwave filter is configured to connect a first microwave transmission line to a second microwave transmission line, configured such that a signal propagates from the first microwave transmission line to the second microwave transmission line. The microwave filter encompasses a highpass component of filter disposed in a symmetrical configuration with respect to a median plane placed perpendicular to the surface of the substrate, including the central axis of the first and second microwave transmission lines; and a lowpass component of filter connected parallel with the highpass component of filter, the lowpass component of filter being disposed in a symmetrical configuration with respect to the median plane.

1. A microwave filter disposed on a substrate configured to connect a first microwave transmission line to a second microwave transmission line, configured such that a signal propagates from the first microwave transmission line to the second microwave transmission line, comprising:
 a highpass component of filter disposed in a first symmetrical configuration with respect to a longitudinal median plane placed perpendicular to the surface of the substrate, the longitudinal median plane including a central axis of the first and second microwave transmission lines; and  
 a lowpass component of filter connected in parallel with the highpass component of filter, the lowpass component of filter being disposed in a second symmetrical configuration with respect to the longitudinal median plane,  
 wherein the first and second symmetrical configurations are defined on a cross-sectional plane perpendicular to the central axis.  
 
   
   
     2. The microwave filter of  claim 1 , wherein the highpass and the lowpass components of filter are vertically aligned along the longitudinal median plane. 
   
   
     3. The microwave filter of  claim 1 , wherein the highpass component of filter comprises a plurality of capacitive elements laterally arranged along the surface of the substrate, configured such that the geometrical configuration of the capacitive elements is symmetrical with respect to the longitudinal median plane. 
   
   
     4. The microwave filter of  claim 3 , wherein the highpass and lowpass components of filter are laterally aligned along the surface of the substrate such that the lowpass component of filter is disposed inner side of the geometrical configuration of the capacitive elements. 
   
   
     5. The microwave filter of  claim 4 , wherein both side surfaces of the lowpass component of filter is in contact with and electrically isolated from the side surface of the capacitive elements. 
   
   
     6. The microwave filter of  claim 1 , wherein the lowpass component of filter comprises a plurality of resistive elements laterally arranged along the surface of the substrate, configured such that the geometrical configuration of the resistive elements is symmetrical with respect to the longitudinal median plane. 
   
   
     7. The microwave filter of  claim 6 , wherein the highpass and lowpass components of filter are laterally aligned along the surface of the substrate such that the highpass component of filter is disposed inner side of the geometrical configuration of the resistive elements. 
   
   
     8. The microwave filter of  claim 1 , wherein the lowpass component of filter comprises an inductive element. 
   
   
     9. A microwave filter inserted in a microwave transmission line disposed on a substrate, comprising:
 a highpass component of filter disposed on the substrate; and  
 a lowpass component of filter disposed on the substrate,  
 wherein topological distributions of the highpass and lowpass components of filter are approximately same in a mirror-image relationship with respect to a longitudinal median plane, the longitudinal median plane being placed perpendicular to the surface of the substrate and including a central axis of the microwave transmission line along a signal propagation direction, and wherein the topological distributions are defined on a cross-sectional plane, which is perpendicular to the signal propagation direction.  
 
   
   
     10. A microwave filter comprised of thin film elements, the microwave filter being inserted in a microwave transmission line disposed on a substrate and comprising:
 first and second highpass elements disposed on the opposite sides of a longitudinal median plane respectively, the longitudinal median plane placed perpendicular to the surface of the substrate and including a central axis of the microwave transmission line along a signal propagation direction; and  
 a lowpass element disposed on the central axis of the microwave transmission line and sandwiched by the first and second highpass elements with a gap width provided on both sides of the lowpass element, respectively,  
 wherein a topological distribution of the lowpass element is approximately same in a mirror-image relationship with respect to the longitudinal median plane on a cross-sectional plane, the cross-sectional plane being defined as a plane perpendicular to the signal propagation direction.  
 
   
   
     11. A microwave filter comprised of thin film elements, the microwave filter being inserted in a microwave transmission line disposed on a substrate and comprising:
 first and second highpass elements disposed on the opposite sides of the longitudinal median plane respectively, the longitudinal median plane being placed perpendicular to the surface of the substrate and including a central axis of the microwave transmission line along a signal propagation direction; and  
 first and second lowpass elements disposed on the opposite sides of the longitudinal median plane respectively, an arrangement of the first and second lowpass elements being sandwiched by the first and second highpass elements with a gap width provided on both sides of the arrangement of the first and second lowpass elements, respectively,  
 wherein the arrangement of the first and second lowpass elements is approximately same in a mirror-image relationship with respect to the longitudinal median plane on a cross-sectional plane, the cross-sectional plane being defined as a plane perpendicular to the signal propagation direction.  
 
   
   
     12. A microwave filter comprised of thin film elements, the microwave filter being inserted in a microwave transmission line disposed on a substrate and comprising:
 first and second lowpass elements disposed on the opposite sides of the longitudinal median plane respectively, the longitudinal median plane being placed perpendicular to the surface of the substrate and including a central axis of the microwave transmission line along a signal propagation direction; and  
 a highpass element disposed on the central axis of the microwave transmission line and sandwiched by the first and second lowpass elements with a gap width provided on both sides of the highpass element, respectively,  
 wherein a topological distribution of the highpass element is approximately same in a mirror-image relationship with respect to the longitudinal median plane on a cross-sectional plane, the cross-sectional plane being defined as a plane perpendicular to the signal propagation direction.  
 
   
   
     13. A microwave filter, the microwave filter inserted in a microwave transmission line disposed on a substrate, comprising:
 a lowpass thin film element and a highpass thin film element stacked on the lowpass thin film element,  
 wherein topological distribution of a stacked structure comprised of the lowpass and highpass thin film elements is approximately same in a mirror-image relationship with respect to a median plane, the median plane being placed perpendicular to the surface of the substrate, including the central axis of the microwave transmission lines along a signal propagation direction, and wherein the topological distribution is defined on a cross-sectional plane, which is perpendicular to the signal propagation direction.  
 
   
   
     14. A microwave integrated circuit comprising:
 a substrate;  
 a first microwave transmission line implemented by the substrate;  
 a second microwave transmission line implemented by the substrate, configured such that a signal propagates from the first microwave transmission line to the second microwave transmission line;  
 a highpass component of filter disposed in a symmetrical configuration with respect to a longitudinal median plane placed perpendicular to the surface of the substrate, the longitudinal median plane including a central axis of the first and second microwave transmission lines, wherein the highpass component of filter is disposed on the substrate and connects the first microwave transmission line to the second microwave transmission line; and  
 a lowpass component of filter connected in parallel with the highpass component of filter, the lowpass component of filter being disposed in a symmetrical configuration with respect to the longitudinal median plane, wherein the lowpass component of filter is disposed on the substrate and connects the first microwave transmission line to the second microwave transmission line.  
 
   
   
     15. The microwave integrated circuit of  claim 14 , further comprising an active element integrated on the substrate so that the signal is supplied from the second microwave transmission line to the active element. 
   
   
     16. A microwave integrated circuit comprising:
 a substrate;  
 a first microwave transmission line implemented on the substrate, comprising a first signal line, first and second gland patterns sandwiching the first signal line to define a constant gap width along both sides of the first signal line so as to implement a first coplanar waveguide;  
 a second microwave transmission line implemented on the substrate, configured such that a signal propagates from the first microwave transmission line to the second microwave transmission line, the second microwave transmission line comprising a second signal line, the first and the second gland patterns sandwiching the second signal line to define the constant gap width along both sides of the second signal line so as to implement a second coplanar waveguide;  
 a highpass component of filter disposed in a symmetrical configuration with respect to a median plane placed perpendicular to the surface of the substrate, the median plane including a central axis of the first and second microwave transmission lines, wherein the highpass component of filter is disposed on the substrate and connects the first microwave transmission line to the second microwave transmission line; and  
 a lowpass component of filter connected in parallel with the highpass component of filter, the lowpass component of filter being disposed in a symmetrical configuration with respect to the median plane, wherein the lowpass component of filter is disposed on the substrate and connects the first microwave transmission line to the second microwave transmission line.  
 
   
   
     17. The microwave integrated circuit of  claim 16 , wherein both of facing edges of the first and second signal lines fork into a plurality of branch lines including three or more branch lines, respectively. 
   
   
     18. The microwave integrated circuit of  claim 17 , wherein the first signal line disposed on the substrate and a gland plate is disposed under the substrate so as to implement a first microstrip line sandwiching the substrate between the first signal line and the gland plate, and the second signal line is disposed on the substrate so as to implement a second microstrip line sandwiching the substrate between the second signal line and the gland plate.